I don't think a coin expert would be much help here. When a expert analyzes a coin, they compare it to a genuine coin and examine the subject coin for signs of forgery. For example, a forged coin might be a slightly different color because it uses a different alloy than the real coin. Or maybe the thickness or the weight is wrong, because a different material was used or there is a "filler" material inside of it (even if the outside is the right metal.) Some coins have micro-engraving that might be missing on a forged coin, because that's hard to replicate.
But all of this depends on having a genuine coin to compare it to. This is, apparently, a one-of-a-kind coin - and unless John Titor starts driving Uber, there's no way to hop over to that parallel dimension and get a real one. What makes it a "coin" and not just a hunk of metal is that it has certain verifiable features that make it legal tender. But you can't know if that's the case here because there is no control sample to compare it to.
When coins are produced at The Mint, they're produced with certain and very strict percentages
of the metals used to produce them and they are all held to that procedure.
All that would be needed is scrapings from said coin to tell a forgery from a reality.
If the metals are all solid but NOT on the books,
it would be proof enough to tell it was a one-off kind of coin.
However, that alone would still not prove it was from the future,
but quite possibly a brilliantly made forgery.
It all would depend on the metallic ingredient(s) found.
As for most forgery with coins...Some are ground in half and remade into a fake.
People have done this in the past making some of the first Two-Headed coins.
How Are Two-Headed Coins Made? Two-headed coins are made by taking two identical coins of the same denomination and machining them to approximately half the thickness of the original coin. The two halves are then fused together by either welding or soldering the two halves together. (Jul 14, 2022)
Source: This Is the Value of Double-Headed Quarter or Two-Tailed Coins.